Here's the latest list of Porsche approved tires for the Cayenne S and Turbo (please be aware that ALL the mentioned tires have the N0 specification and that they're not the standard versions of the specific tire brand and type):

18'' (235/60 107 All Terrain and 255/55 109 all others):
Pirelli Scorpion AT (Speed Index T) All Terrain
Bridgestone Turanza ER30 (Speed Index Y) Summer
Continental 4x4 Sport Contact (Speed Index Y) Summer
Pirelli P Zero Rosso (Speed Index Y) Summer
Continental 4x4 Contact (Speed Index V) All Season
Pirelli Scorpion Zero (Speed Index V) All Season

19''(275/45 108) and 20"(275/40 106):
Michelin 4x4 Diamaris (Speed Index Y) Summer
Continental 4x4 Sport Contact (Speed Index Y) Summer
Pirelli P Zero Rosso (Speed Index Y)

Porsche highly recommends using ONLY these tires because only these tires have been extensively tested under all driving conditions, including extreme ones.